In conventional image forming apparatuses adopting an electrophotographic process, an electrostatic latent image is formed on a photosensitive drum (image carrying member) having been electrostatically charged uniformly, and the electrostatic latent image is developed into a toner image to form an image on a sheet (recording medium).
The photosensitive drum is provided with sintered bearings in opposite end parts of it. When the photosensitive drum is fitted to a unit case, the sintered bearings each make contact with an electrode chip provided on the unit case. The electrode chip is formed of a sintered member, and is connected to the main body of an image forming apparatus via a ground lead or the like. This permits conduction to the ground (earthing) of slight electric charge remaining on the photosensitive drum after toner image transfer.
For example, Patent Document 1 discloses a drum holding structure that includes an electrode chip which is in sliding contact with a sintered copper portion arranged in an end part of a photosensitive drum and which is formed of a sintered copper member to make the photosensitive drum electrically conductive, an accommodation recess formed in a holder to accommodate the electrode chip, a spring which elastically biases the electrode chip to keep it in contact with the sintered copper portion, and a stopper which keeps the protruding amount of the electrode chip from the accommodation recess at a predetermined amount.
Patent Document 2 discloses a configuration in which core bars of two brush rollers for scraping off toner remaining on the surface of an image carrying member are short-circuited with each other via two sintered bearings which support the two core bars respectively and a flat spring which makes contact with the sintered bearings. A method is also known in which the configuration of Patent Document 2 is applied to a photosensitive drum to keep a sintered bearing fitted to a flange portion of the photosensitive drum and the photosensitive drum pipe in contact with each other via the flat spring and to keep the sintered bearing and the drum shaft in sliding contact with each other so that mutual electrical conduction between the photosensitive drum and the drum shaft is secured.